SAN FRANCISCO – Big Dog, a four-legged robot that can climb muddy hills, and Cheetah, a robot which can outrun the fastest human, are among the robots that now belong to Google Inc.

The world’s largest Internet search company acquired Boston Dynamics, a privately held company best known for building robots that look as if they belong in a science-fiction movie and which are often co-developed or funded by the U.S. military.

The acquisition is the latest by Google’s secretive robotics division, led by Andy Rubin, the former boss of the company’s Android mobile operating system. Google’s new robotics division has acquired more than a half-dozen other robotics companies.

Google declined to comment and Boston Dynamics did not return requests for comment. A person familiar with the matter confirmed the deal, which was first reported by the New York Times on Saturday, and said that Google will honor Boston Dynamics’ military contracts.

The financial terms of the deal could not be learned.

Based in Waltham, Massachusetts, Boston Dynamics was founded in 1992 as a spin-off from the Massachusetts Institute of Technology. The company works with the U.S. Army, Navy, Marine Corps and the Defense Department’s Advanced Research Projects Agency, according to its website.

The company’s website lists a catalog of nine different robots, including a DARPA-funded machine capable of scaling vertical walls using “micro-claws,” and a small four-wheeled vehicle that can jump 30 feet into the air and which is being developed with the U.S. Army’s Rapid Equipping Force.

The four-legged Cheetah robot, which can surpass speeds of 29 miles per hour according to the website, is billed as the “fastest legged robot in the world.”

Google has been tight-lipped about what it plans to do with the robots. Media reports earlier this month suggested that the company’s efforts were focused on developing robotics technology that can be used in factories.